Invasion of erythrocytes by malarial merozoites requires specific determinants on the surface of erythrocytes to which merozoites attach. Low affinity receptors mediate the initial interaction and apical reorientation; high affinity receptors form an apical junction that precedes entry into the parasitophorous vacuole. Previous studies on Plasmodium knowlesi have shown that the Duffy blood group determinant is involved in junction formation, the high affinity binding. We have now shown that band 3, the major erythrocyte transmembrane protein, is receptor and is probably involved in the initial recognition. We are now attempting to identify equivalent receptor components on merozoites.